Fix'n VT220s

YEs, and I still do :-). Fortunately, as I said, it is unlikely that a good CRT would be amaged by putting it into siad terminal. It's just that it takes a long time ot swap it, and you're wasting the time if that's not the fault. I said 'unlikely' to damage the new CRT. Actually, those all-glass pin bases are somwaht fragile, and continually fitting and remvoig nthe socket may damage a seal. I've ruined a few B7G andB99A (7 pin miniature and Noval) vlaves over the years in this way. So it's best not to remvoe the CRT without a good reason. Oh, I must have mis-read what you said. I thought you sid the CRT looked perfect. A white one and a colour filter :-) The old CRT might take being boosted. It's unlikely, modern-ish CRETs don;'t normally repsond too well, but if the CRT is dead anyway, you can't make things much worse. BASically, over-run the heater as much as you dare (15 or 18V) and apply a high votlage (a few hundred volts) with a current limiting resisotr (a few mA) between the carthode and control grid (grid +ve in this case). There ahve been designes for CRT boosters in various magazines over the years, there are probably designs on the web. The idea is to rip the top layer off the cathode, exposing better emissive material. Problem is that modern cathodes don't have much left if you try this. You may well end up with a CRT that gies no emission at all. I don't thing I've seen that one. The VT220s I've worked onhad all the ICs in DIL packages. I do recall PLCC ICs in the VT3xx terminals, I wonder if the design is similar ot one of thsoe. -tony